I'll see how it goes there; I suspect that even if I get it to do its full potential it'll still seem pretty lacklustre compared to the ~300k hps I pull on AG-friendly fights :P
Slightly off topic, but which fights are you getting the best results from AG on? I've been trying to find ways to work it in, but there aren't any fights where rushing streams is bad so I haven't been experimenting much yet.
Well, first we have to define "best".
My definition of best: "Delivers the healing when it is needed most"
I use AG for Protectors
(during Dark Meditation, or sometimes to deal with Inferno Blast/Calamity overlaps), Norushen
, Normal Sha of Pride
(but not Heroic because we're too spread), Galakras
(during Korgra the Snake and again at the end with Flames of Galakrond), Malkorok
(for Blood Rage healing; I raid with 4 priests who just each pop Halo at the start of the fight and everyone's shield is full), and Garrosh
(for Ironstar Explosions and Whirling Corruptions).
I was using AG for Thok, because I could get off Healing Surges between the Deafening Screech casts and use AS to get an instant HR down. But I have been experimenting with Conductivity instead - practicing for Heroic Thok - and I really like it. I'm torn there which will be more useful until I try it.
For the remaining fights I use RS and wear 2p Ht15/2p t16. Mind you, I'm in 25-player raids, so even with RS and the tier 15 2-piece bonus, I'm only ever covering 12% of my raid with each tick of Healing Stream, whereas I can see it being a lot stronger in 10-player raids where it covers 30%.
Rushing Streams will very likely generate more healing than Ancestral Guidance will, so if all you care about is raw throughput, then you can stick with it for all the fights. However, I'm one of those old-school BC healers who believes that healing is about responding to damage patterns, and Ancestral Guidance allows you to respond to burst damage while Rushing Streams really does not. :)